(a) Field of the Invention
The present invention relates to a learning method and a learning apparatus for controlling opening or closing of an intake/exhaust valve of a vehicle, more particularly, to a learning method and a learning apparatus capable of preventing noise that occurs upon learning a changed area of an inflow passage of the intake/exhaust valve, in order to avoid discomfort to vehicle occupants, and improve marketability of the vehicle.
(b) Description of the Related Art
A vehicle to which a diesel engine is applied includes a plurality of intake/exhaust valves. Types of intake/exhaust valves include: an exhaust gas recirculation valve (EGR valve), an air control valve (ACV), a swirl control valve (SCV), etc.
Among those, the EGR valve serves to control the amount of exhaust gas re-circulated to the intake side of the engine, in an exhaust gas recirculation (EGR) system that re-circulates some of the exhaust gas to an intake manifold to reduce NOx occurring at a high temperature in the exhaust gas.
However, if various kinds of incomplete combustion materials included in the exhaust gas are introduced into the intake side of the engine by the EGR, soot is deposited at a portion of an inflow passage of the foregoing EGR valve. Therefore, the inflow passage of the EGR valve is continuously narrow and the amount of re-circulated exhaust gas is reduced. Accordingly, upon mapping a control map determining whether to open and close the EGR valve, an emission is likely to exceed a reference value.
To prevent this, as illustrated in FIG. 2 (RELATED ART), the vehicle to which the existing diesel engine is applied forcibly opens and closes repeatedly the EGR valve whenever the engine stops and then recognizes a pressed amount of the valve in a state in which the valve is closed, thereby continuously monitoring and learning the soot deposition of the inflow passage of the EGR valve and an area of the inflow passage of the EGR valve accordingly. That is, the mapping value of the control map controlling the opening and closing of the EGR value is changed in response to the area of the inflow passage of the EGR valve that is narrow due to the soot deposition.
Further, a swirl control valve (SCV) serves to quicken a flow of air in a combustion chamber of the diesel vehicle. That is, the SCV is a valve that is installed in a suction hole and changes a direction of the valve to change an intake port to a swirl port or uses a general intake port to improve power and a fuel consumption rate.
To reduce an ignition delay of the diesel engine, there is a need to increase an intake flow rate and a flame speed. If the intake flow rate in the combustion chamber is quick, a mixture of air and fuel is good and the flame speed is also quick. Therefore, if the uniform mixture is made quickly, the generation of particulate matter (PM) is reduced. However, the general diesel engine has problems in that an up-and-down motion of a piston is slow during low-speed driving, and therefore the intake flow rate is slow and it is difficult to perform the smooth mixture.
To solve the above problems, the existing diesel engine has two small intake ports and uses the SCV to operate the engine in the state in which one intake port is closed. For example, the SCV is closed to quickly perform the mixture in an idle state/a middle-low load region (3000 rpm or less) where the flow rate is slow, and the SCV is open in a high load region (3000 rpm or more) to increase the engine power in response to an increase in charging efficiency and a reduction in pumping loss.
Further, an air control valve (ACV) serves to reduce vibration of the diesel engine upon a key-off. For example, the diesel engine is operated by inertia even after the key-off. In this case, the fuel that is injected into the engine in advance is combusted by the operation of the engine as described above. As described above, vibration occurs by the combustion of the engine that occurs after the key-off. To prevent this problem, there is a need to cut off the intake temporarily supplied to the engine upon the key-off. The valve performing this role is the air control valve (ACV).
However, various kinds of incomplete combustion materials that are included in the exhaust gas are sucked into an intake manifold through the EGR. In this case, some of oil mist is stuck to the inflow passage of the SCV and the ACV, and therefore the inflow passage is continuously narrow. Therefore, upon mapping the control map determining whether to open and close the SCV and the ACV, an emission is likely to exceed a reference value.
To prevent this problem, as illustrated in FIG. 3 (RELATED ART), the vehicle to which the existing diesel engine is applied forcibly opens and closes repeatedly the SCV and the ACV whenever the engine stops and then recognizes the pressed amount of the valve in the state in which the valve is closed, thereby continuously monitoring and learning the impurity deposition of the inflow passage of the SCV and the ACV and the area of the inflow passage of the SCV and the ACV accordingly. That is, the mapping value of the control map controlling the opening and closing of the SCV and the ACV is changed in response to the area of the inflow passage of the SCV and the ACV that is narrow due to the impurity deposition.
As described above, the intake/exhaust valves (EGR valve, SCV, ACV, etc.) of the vehicle to which the existing diesel engine is applied learn the changed area of the inflow passage whenever the key-off is made. That is, the mapping value of the control map is changed in response to the changed area of the inflow passage. Further, before the area of the inflow passage is changed, the intake/exhaust valves (EGR valve, SCV, ACV, etc.) are opened and closed several times to tramp the impurities and then perform the learning, thereby minimizing the error of the changed area of the inflow passage (see, e.g., FIG. 1 (RELATED ART)).
However, unnecessary noise occurs during the learning and the opening and closing before the learning, such that vehicle occupants may experience discomfort, and the marketability of the vehicle may be reduced.